Its first version was called the HCTL, and has been discontinued; it was replaced by the HCTL, that essentially has a lower power consumption, and has had a few non essential features added, such as the possibility of presetting the position registers this can be taken care of in software , and of synchronizing more than one motor. Now these products are carried by Agilent Technologies. Miscellaneous application notes on interfacing the chip to various micro controllers. Re print of a paper that appeared in Electronics Design a few years ago. List of manufacturers that used the chip to build motion control systems.
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Position and Velocity Control? Programmable Digital Filter and Commutator? TTL Compatible? It frees the host processor for other tasks by performing all the time-intensive functions of digital motion control.
The programmability of all control parameters provides maximum flexibility and quick design of control systems with a minimum number of components. No analog compensation or velocity feedback is necessary. HCTL vs. Some differences exist, and some enhancements have been added. Supply Current Max. Power Dissipation Max. The HCTL receives its input commands from a host processor and position feedback from an incremental encoder with quadrature output.
The encoder feedback is decoded into quadrature counts and a bit counter keeps track of position. The HCTL executes any one of four control algorithms selected by the user. The four control modes are:? Position Control? Proportional Velocity Control? Trapezoidal Profile Control for point to point moves? Integral Velocity Control with continuous velocity profiling using linear acceleration The HCTL has the capability of providing electronic commutation for DC brushless and stepper motors. Using the encoder position information, the motor phases are enabled in the correct sequence.
In addition, phase overlap and phase advance can be programmed to improve torque ripple and high speed performance. The HCTL contains a number of flags including two externally available flags, Profile and Initialization, which allow the user to see or check the status of the controller. It also has two emergency inputs, Limit and Stop, which allow operation of the HCTL to be interrupted under emergency conditions.
The HCTL controller is a digitally sampled data system. While information from the host processor is accepted asynchronously with respect to the control functions, the motor command is computed on a discrete sample time basis. The sample timer is programmable. The HCTL compares the desired position or velocity to the actual position or velocity to compute compensated motor commands using a programmable digital filter D z.
Internal Block Diagram. Figure 2. Operating Mode Flowchart. Two channels, A and B, 90 degrees out of phase are required. Index Pulse — Input from the reference or index pulse of an incremental encoder. Used only in conjunction with the Commutator.
Either a low or high true signal can be used with the Index pin. See Timing Diagrams and Encoder Interface section for more detail. Address Latch Enable — Enables lower 6 bits of external data bus into internal address latch. For a Write, the external bus data is written into the internal addressed location. For Read, data is read from an internal location into an internal output latch. Output Enable — Enables the data in the internal output latch onto the external data bus to complete a Read operation.
Motor Command is set to zero. Status of the Limit flag is monitored in the Status register. Stop Flag — An internal flag that is externally set. Reset — A hard reset of internal circuitry and a branch to Reset mode. Not connected. These pins should be left floating. MC7 is the most significant bit MSB. Profile Flag — Status flag which indicates that the controller is executing a profiled position move in the Trapezoidal Profile Control mode.
When this pin is pulled low, the internal sample timer is cleared and held to zero. When the level on the pin is returned to high, the internal sample timer instantly starts counting down from the programmed value.
A low level on this input pin causes the internal Limit flag to be set. If it is not connected, the pin could float low, and possibly trigger a false emergency condition. In general, the user should clear all control mode flags after the limit pin has been pulled low, then proceed. When a low level is present on this emergency-flag input, the internal stop flag is set. When the STOP flag is set, the system will come to a decelerated stop and stay in this mode with a command velocity of zero until the Stop flag is cleared and a new command velocity is specified.
Notes on Limit and Stop Flags Stop and Limit flags are set by a low level input at their respective pins. The flags can only be cleared when the input to the corresponding pin goes high, signifying that the emergency condition has been corrected, AND a write to the Status register R07H is executed. That is, after the emergency pin has been set and cleared, the flag also must be cleared by writing to R07H.
Any word that is written to R07H after the emergency pin is set and cleared will clear the emergency flag. The lower four bits of that word will also reconfigure the Status register. Channels A and B are internally decoded into quadrature counts which increment or decrement the bit position counter. For example, a count encoder is decoded into quadrature counts per revolution.
The position counter will be incremented when Channel B leads Channel A. The Index channel is used only for the Commutator and its function is to serve as a reference point for the internal Ring Counter. The designer should therefore generally avoid creating the encoder pulses of less than 3 clock cycles.
The index signal of an encoder is used in conjunction with the Commutator. It resets the internal ring counter which keeps track of the rotor position so that no cumulative errors are generated. The Index pin is active low and level transition sensitive. It detects a valid high-to-low transition and qualifies the low input level through the 3-bit filter.
At this point, the Index signal is internally detected by the commutator logic. This type of configuraiton allows an Index or Index signal to be used to generate the reference mark for commutator operation as long as the AC specifications for the Index signal are met. MC7 is the most significant bit. During any of the four Control modes, the controller writes the motor command into R08H. The PWM port outputs the motor command as a pulse width modulated signal with the correct polarity.
This flag is also represented by bit 0 in the Flag Register R00H. Both the Pin and the Flag indicate the status of a trapezoid profile move.
When the HCTL begins a trapezoid move, this flag is set by the controller a high level appears on the pin , indicating the move is in progress.
When the HCTL finishes the move, this flag is cleared by the controller. Note that the instant the flag is cleared may not be the same instant the motor stops. The flag indicates the completion of the command profile, not the actual profile. If the motor is stalled during the move, or cannot physically keep up with the move, the flag will be cleared before the move is finished. This pin is internally connected to the software flag bit 5 in the Status Register R07H.
The four pins can be programmed to energize each winding on a multiphase motor. These registers contain command and configuration information necessary to properly run the controller chip. The 35 user-accessible registers are listed in Tables 1 and 2. The register number is also the address. A functional block diagram of the HCTL which shows the role of the useraccessible registers is also included in Figure 3.
The other 29 registers are used by the internal CPU as scratch registers and should not be accessed by the user. Figure 3. Register Block Diagram. Register Hex Dec. Consult appropriate section for data format and use.
Upper 4 bits are read only. The scalar data is limited to positive numbers 00H to 7FH. Each flag is set and cleared by writing an 8-bit data word to R00H. The flag is reset by the controller when the move is completed. The user should not attempt to set or clear F1. When set, this flag inhibits the internal commutator counters to allow open loop stepping of a motor by using the commutator.
Bit 3 indicates whether to set or clear a certain flag, and bits 0,1,and 2 indicate the desired flag. A soft reset writing 00H to R05H will not reset the flags in the flag register. The flags can also be reset by writing the proper word to the Flag register as explained above.
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It frees the host processor for other tasks by performing all the time-intensive functions of digital motion control. The programmability of all control parameters provides maximum flexibility and quick design of control systems with a minimum number of components. No analog compensation or velocity feedback is necessary. Note: Avago Technologies encoders are not recommended for use in safety critical applications. Supply Current 30 mA mA Max.